1. Field of the Invention
The present invention relates to a timing controller, a liquid crystal display device having the same, and a driving method thereof, and more particularly, to a timing controller capable of adjusting luminance of maximum gradation according to an amount of white of image data to thus enhance screen quality and reduce power consumption of a liquid crystal display device, a liquid crystal display device having the same, and a driving method thereof
2. Description of the Related Art
A display device, a visual information transmission medium, refers to a device visually displaying data in the form of characters or diagrams on a surface of a Braun Tube.
In general, a flat display panel (FPD) device as an image display device which is thinner and more lightweight than a TV or a CRT (Cathode Ray Tube) includes a liquid crystal display (LCD) using liquid crystal, a plasma display panel (PDP) using gas discharge, an organic light emitting diode (OLED) device using an organic material based on a phenomenon that when a current flows to a phosphor organic compound, light is emitted, an electric paper display (EDP) using a phenomenon that charged particles within an electric field moves toward a positive electrode or a negative electrode, and the like.
An LCD device, one of the most typical FPD devices, displays a desired image by adjusting light transmittance of pixels arranged in an active matrix form by individually supplying data signals according to image information to the pixels.
Such an LCD device includes a liquid crystal panel for displaying image data provided from the outside and a driving circuit for driving the liquid crystal panel.
Meanwhile, in case of a CRT or a PDP, among the conventional display devices, when the amount of white is increased in an image data, luminance of white is gradually reduced, but in case of an LCD device, although the amount of white in image data is increased, the same level of white luminance is maintained.
Thus, when an amount of white over the entire screen is assumed to be, for example, 40%, maximum luminance may be maintained at 450 nit, implementing brighter and more sharp picture quality relative to a CRT or a PDP.
However, as mentioned above, when the amount of white is increased in image data, a bright image dazzles the user's eyes and makes the user feel easily tired, and a rather too brighter and stimulating image is displayed relative to a CRT or a PDP.
Also, when the amount of white is increased in image data in the LCD, since the same level of white luminance is maintained, luminance is unnecessarily maintained, resulting in a waste of power.
In order to solve this problem, various techniques for reducing screen luminance have been presented. One of the techniques is an average picture level (APL) technique. According to APL technique, gray level values corresponding to image data are added up and the sum is divided by the number of image data to obtain an average gray level value of the image data, and luminance of a backlight unit is set accordingly.
However, in the case of the APL technique, backlight luminance of even an image in which image data has a high average gray level value is lowered, rather than a bright image having a great deal of white components in image data, degrading picture quality as an advantage of an LCD screen. Namely, a maximum output of the backlight unit is lowered to reduce a difference in luminance between gray levels in a high gray level region, resulting in a degradation of picture quality.